In a Long Term Evolution (LTE) system, phase noise independent of Gaussian white noise may occur during a transmission signal of a User Equipment (UE) or an evolved Node B (eNB) is being processed. The phase noise refers to such a random change in phase of a signal output by the system (such as various radio frequency devices) that arises from various noises in the system.
Since there is a random change in phase of the transmission signal due to the phase noise, the phase noise may impose some negative influence on demodulation of a received signal, e.g., on a calculation result of a Log-Likelihood Ratio (LLR), and may impose a larger negative influence thereon at a higher level of Modulation and Coding Scheme (MCS), and for example, the precision of calculating an LLR may be higher at a higher level of MCS, where there is a higher transmission rate of communication at a higher level of MCS.
In the prior art, the eNB generally demodulates the received signal in the following schemes.
In a first scheme, the eNB regards the received signal equivalently as a signal of a standard constellation point, onto which noise in a complex Gaussian distribution is superimposed, i.e., Gaussian white noise, and then calculates an LLR of the received signal.
However only the Gaussian white noise is taken into account, but the phase noise is not treated correspondingly in the first scheme, so the calculated LLR may not be precise.
In a second scheme, the phase noise is introduced to a constellation point of the transmission signal, and then the LLR of the received signal is calculated.
However when the phase noise is verified in the second scheme, the reception performance of a receiver may be degraded, and the demodulation efficiency may be lowered.